The hippogryph was saved the first time as well. If you remember the second time the executioner used the axe to cut a pumpkin, that is what Ron, Harry, and Hermoine saw the first time around, not him actually kill Buckbeak. They just saw the axe raise up and go down

yeah, he was saved the first time by harry and hermione with the time turner.. so how isnt it possible that they saved everyone else with the time turner, so like when they see someone die they see them like fall down and dissapear or somethign, not die.. basically its ********.

It would be a bit far fetched to save everyone like that, think space time continuum. If you go back in time and kill hitler before he rises to power, you have to make a note to the future you to go back and kill this now seemingly random guy. In the Harry Potter universe if you go back in time to kill voldemort you have to do the same thing. It would work, but you have to be willing to follow random notes that claim to be from the future (I'm assuming that for some reason you don't want to run into your current self or change other parts of the past)